material. Through the analysis of the influence of the position and amount of ceramics in the armor against the elastic energy, a composite armor structure with the best “cost-effectiveness†ratio was proposed.
Ceramic materials are excellent armor materials due to their high dynamic strength, high hardness, and low density. They not only have good protective properties for small-diameter kinetic energy bombs, but also rod-type kinetic energy bombs and armor-piercing bombs. But ceramics also have their fatal weaknesses, that is, its price is very expensive.
The price of alumina ceramics is more than one to twenty times that of armored steels, and the prices of ceramics such as silicon carbide, silicon nitride, and boron carbide are higher (Table 1). The high cost of ceramics limits its application, especially on the main battle tanks. This situation is similar to that of titanium alloy armor. Although titanium alloy armor has excellent resistance to elasticity, its high price makes its application limited to aerospace and aerospace.
Table 1 Properties of ceramics suitable for use in armoring Materials Density Young's modulus M Relative price Alumina (with Ab385%) Alumina (with A丨2O3%%) Boron carbide Diboride Titanium carbide Siliconized glass ceramic Oxide oxide Composite armor When choosing a ceramic, not only does it have to be based on the performance of the ceramic, but also more importantly according to its price. Due to the high price of ceramics, it should be placed in the position of the composite armor that can best play its role, and at the same time, the amount should be reduced as much as possible so that the composite armor can achieve the maximum cost-effectiveness ratio.
Heavy-duty ceramic armor is mainly used in main battle tanks. Its protective objects are large-diameter armour-piercing bombs and large-caliber kinetic energy bombs.
Ceramics have a strong erosion effect on the armor jet, and the high dynamic strength of the ceramic makes the diameter of the crater generated by the jet in the ceramic very small, thereby increasing the interference effect on the jet and improving the protective effect.
Long-arm penetrators are similar to the armored jet in setting the ceramics at high speeds. Ceramics with good anti-stripping jets also have good anti-elastic properties for long rod piercing bullets.
1 Types of ceramics Gary Savage proposes that the resistance to elasticity of ceramic materials is measured by the value of /W. The value of M is calculated by the following formula. Although the physical meaning of the M value of ceramics is not clear, the elastic and Young's modulus and hardness of ceramics The density-related conclusions are still correct. From the standpoint of resistance to elasticity, ceramics such as silicon carbide, silicon nitride, and titanium diboride are all superior to alumina ceramics, but considering the price, the only ceramic used in heavy-duty ceramic armor at home and abroad is alumina ceramic.
2 Position and amount of ceramic In order to maximize the protective effect of ceramic materials, the composite armor obtains the maximum effect-cost ratio, in heavy-duty ceramic armor, except for -07-20; Revised flood season: 200 Bu 09-13: Cui Lin , Female and senior workers have to choose high-efficiency ceramic materials, but also to correctly arrange the position of ceramic materials in the composite armor, and to reasonably determine the amount of ceramic materials.
When the penetration velocity of the jet is greater than the crack growth rate of the ceramic, the ceramic material at the bottom of the crater can maintain the integrity and can exert the strength effect of the ceramic. On the contrary, when the penetration velocity of the jet is less than the crack propagation speed of the ceramic, the ceramic material at the bottom of the crater has been broken, so that its anti-elastic energy is reduced. Therefore, the ceramic material should be placed on the front of the composite armor to counter the high-speed segment of the armor jet.
The armor jets were tested and the results were obtained. The target consists of a 20mm steel panel and several 20-sheet backplates. The middle is composed of a 1mm-thick glass sandwich. The interlayer thickness is 20mm to 360mm. And the ordinate is the isobaric wear depth, abscissa It is the thickness of the glass interlayer and is the blank penetration depth of the armor jet. From and to see, with the increase in the thickness of the glass, the depth of penetration of the isobar of the target plate drops first, and then rises through a low point. The descending segment indicates that the protective system of all points of the glass is greater than 1, that is, the protective force of glass is higher than the protective force of steel, and the rising segment indicates that the protective coefficient of each point of glass is less than 1, that is, the protective force of glass is lower than the protective force of steel.
In accordance with the protective force of the glass, the result of the 360mm glass separable glass thickness/mm 6 times caliber when bombing high is three parts, the first part from 160mm, this part of the glass has a higher protection force, the second part from 16mm to 200mm, the protective force of this part of the glass is lower than the first part, the third part is from 2mm to 360mm, its protective force is further reduced, and the protective force is lower than the protective force of steel. According to the structure of the test target, in order to obtain the best protection effect, the thickness of the glass should be no more than 200mm or 160mm. Considering the effect-cost ratio, the thickness of the glass should also be reduced.
According to reports, the ceramic crack propagation speed is about one third of the speed of sound. Based on this, the following set of formulae can be used to calculate the maximum thickness of the ceramic used in composite armor: - the longitudinal sound velocity of the ceramic, the Young's modulus of m/s porcelain, the density of Pa-ceramics, g/cm3 - the jet head Velocity, penetration velocity of m/S jet, square root of m/s ceramics and jet density - thickness of ceramic S - distance of virtual point of ceramic to ceramic surface, m - jet initial head velocity, m/s Full chrome corundum ceramic materials for composite armor sandwich and chrome corundum ceramics - glass steel - high hardness steel sandwich for comparison tests, the results are shown in Table 2.
Table 2 Comparison results of different sandwich composite armor å…® Target plate structure thickness Steel original protection plate clamp M backplane coefficient 180mm Chrome corundum: 80mm Road just k A hard steel results show that the use of chrome corundum ceramics - glass steel - high hard steel Instead of chrome corundum ceramics as a composite armor interlayer, not only does the protective performance (protection factor, thickness coefficient) of the composite equipment increase, but also the price is cheaper, so that it has a higher efficiency-cost ratio.
3 Conclusions In terms of cost-effectiveness, alumina ceramics are the best choice for heavy-duty ceramic armor.
Only when the penetration velocity of the jet is greater than the ceramic crack growth rate, the ceramic exhibits a high ballistic resistance, so the ceramic should be placed in front of the heavy composite armor.
Ceramics have a low ability to resist low-velocity jet penetration. Over-thick ceramics reduce the elastic resistance of heavy-duty ceramic armor and limit the amount of ceramic used in composite armor.
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